In general, silver halide color photographic light-sensitive materials are processed by use of a color developer, a bleach, a fixer, a bleach-fixer and a stabilizer. Among these processing solutions, the bleach and bleach-fixer contain a bleaching agent to bleach silver. For this purpose, ethylenediaminetetraacetate ferric complex salts are most widely used at present in processing color paper and color negative films. However, ethylenediaminetetracetate ferric complex salts are poor in biodegradability. If accidently discharged into a river or soil, they are accumulated there for a long time without undergoing degradation and, thereby, pollute the natural environment. Recently, 1,3-propanediaminetetracetate ferric complex salts (PDTA-Fe) described, for example, in Japanese Pat. O.P.I. Pub. Nos. 103041/1990, 103040/1990, 250651/1988 have been used. Although PDTA-Fe has high bleaching power and excellent rapid-processing capability, it causes bleach fogs when bleaching is carried out immediately after color developing. To eliminate the problem, the pH can be lowered by use of acetic acid or the like, but it causes other problems such as offensive smell and higher biochemical oxygen demand.
Another disadvantage of PDTA-Fe is its strong oxidizing power; therefore, thiosulfates used as fixing agent are decomposed into sulfur or sulfides when bleaching with PDTA-Fe is followed by processing with a fixer, or when PDTA-Fe is used as bleaching agent in a bleach-fixer.
Though diethylenetriaminepentaacetate ferric complex salts described, for example, in Japanese Pat. O.P.I. Pub. Nos. 118752/1986, 50145/1986, 50150/1986, 50147/1986 are known as a third bleaching agent, they also have shortcomings.
That is, these are not only poor in biodegradability but also are liable to cause yellow stains on edges of a light-sensitive material when used in processing color paper, particularly in processing carried out at a low replenishing rate.
Bleaching agents described, for example, in EPO, 430,000A1 and German Pat. No. 3,939,756 are known as compounds having high biodegradability, but these bleaching agents are apt to lower the desilverizing property when employed in processing at a low replenishing rate and, as a result, deteriorate the rapid processing capability.
Methods for regenerating a bleach-fixer are described, for example, in Japanese Pat. O.P.I. Pub. Nos. 48245/1991 and 121451/1991. These methods, however, are used for regenerating bleach-fixers by means of a ferric complex salt of an aminopolycarboxylic acid such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, cyclohexanediaminetetraacetic acid or 1,3-diaminopropanetetraacetic acid. These compounds have a disadvantage of poor biodegradability or a tendency to decompose a fixing agent as described above. Therefore, these methods give neither suggestion as to the compound of the invention nor hint as to the effect of the invention described below.